This invention relates to pumps in general and, in particular, to a new and useful pressure gas operated double diaphragm pump.
Known diaphragm pumps include a chamber in a casing which is divided by a transverse diaphragm into two smaller chambers, namely, a pumping chamber and a driving chamber. The driving gas is fed to the driving chamber in pulses under pressure and is ejected again. These gas pulses cause the movement of the diaphragm inside the chamber, so that the pumping chamber is alternately increased and decreased in strokes. Due to these changes in size, the medium to be pumped is moved. Inlet and outlet valves are provided which regulate the direction of motion. The pulsating supply of the driving gas is controlled by means of a valve which receives its pulses from the filling level of the pumping chamber. In order to clearly separate the filling strokes from the discharge strokes, which is necessary for optimum filling, and thus the amount of delivery, known diaphragm pumps include holding means to ensure the movement of the diaphragm from one end position into the other only after the pumping chamber has been filled or emptied.
Another known double diaphragm pump has a pressure medium supply controlled by the position of the diaphragms. In this diaphragm pump, the two diaphragms are rigidly coupled with each other by a rod. This coupling rod has a cam which actuates the control arm of a rotary slide valve with which the pressure gas supply to the driving chambers is then controlled. Alternately, this rotary slide valve is actuated by a spring secured on the coupling rod, over which the rotary slide valve is to be switched obviously in jerks. The object is to achieve snap switching with which complete filling of the respective controlled pumping chamber is to be obtained. The control over the provided spiral springs requires a complicated mechanical design. It is doubtful if the friction of the rotary slide valve remains constant enough that the forces from the total pressure on the diaphragms are sufficient. Only in this way is a uniform switching rhythm ensured after the filling or discharging of the pumping chambers, see French Pat. No. 967,191.
A hydraulically operated double diaphragm pump is also known which consists of two casings arranged in an axis. Each casing is subdivided by a diaphragm into a pumping chamber and into a driving chamber. Both diaphragms are connected with each other by a coupling rod. The chambers which are traversed by the coupling rod serve as driving chambers, with the outer chambers serving as pumping chambers, provided with inlet and outlet valves. A piston valve controls the supply of the hydraulic driving fluid to one of the two driving chambers and the discharge from the other driving chamber. The end positions of the piston valve are fixed by a ball lock whose initial stress is adjustable. The shifting of the piston valve is effected by a rigid arm secured on the coupling rod, which slides over a pin-shaped extension of the piston valve and is connected with the valve in both directions of motion, each by a coil spring. When a driving chamber is filled with driving fluid, its diaphragm curves to the outside and entrains its arm over the coupling rod. The coil spring arranged in the direction of motion is tensioned, while the other is relaxed.
As soon as the spring forces exceed the force of the ball lock, the piston valve is moved into its other end position by the spring forces. The driving fluid can thus issue from the driving chamber, while its supply is switched to the other driving chamber. The transmission of the movement of the coupling rod through an arm and an operating rod to the control rod arranged in a separate casing is very bulky, and the mechanical expenditure for the control requires a very accurate adjustment and continuous control. Particularly critical are the two springs arranged on the operating rod for the control valve, since they must maintain their spring force, or otherwise, the click stop device will possibly no longer work properly, see German Pat. No. 1,453,607.